Field of the Invention
The present invention relates to a liquid ejection head substrate and a semiconductor substrate.
Description of the Related Art
A method for manufacturing an ink jet print head is known, in which an electrode pad is formed on an element substrate by using electrolytic plating (see Japanese Patent Laid-Open No. H11-334076(1999)).
In forming a gold bump on an electrode pad by using electrolytic plating, the following steps are performed in sequence: the step of forming a base layer with a metal material having a high melting point such as titanium tungsten (TiW), the step of forming a gold (Au) (base seed metal) film, the step of applying/exposing/developing a resist, the step of depositing gold by electrolytic plating, the step of stripping a resist, the step of etching the base seed metal, and the step of etching the base layer of a metal material having a high melting point.
In the case of forming a gold bump on a substrate, it is sometimes preferable that a gold film of the gold bump be thin. Specifically, in terms of cost reduction, it is desirable to have a thinner gold film. Furthermore, in laminating organic materials of ink jet nozzle material on a substrate having a thick gold bump formed thereon by a so-called photolithography process, for example, a thick convex portion on the substrate causes decrease in uniformity within the substrate surface. For this reason, there is a need for thinning a gold film.
However, in the case of a thin gold film, the problem is that heat or pressure applied on the gold bump in bonding an external connection portion to the gold bump may cause the gold to be diffused into the side of a conductor layer. If the gold is diffused into the side of the conductor layer, alloying may cause the bump to be less conductive or easily melted, resulting in lower reliability of the bump. To avoid this, bonding conditions may be changed to prevent the gold from being diffused into the side of the conductor layer by lowering heat and pressure. However, change in the bonding conditions may decrease adhesion of the external connection portion to the gold bump.